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by Daniël Janse van Rensburg, PhD, Divisional VP and Chief Technology Officer, NSI-MI Technologies/Ametek

MPD: Please describe what you consider to be your company’s most significant technological achievements.


For the past five decades, NSI-MI Technologies has been at the forefront of commercializing antenna, radome, and radar cross-section test systems. Starting with an initial offering of precision rotary positioners that formed the foundation of our first far-field antenna test systems, we added capabilities like RF instrumentation, compact range reflectors, test software, and anechoic chambers to vertically integrate all the components that allow us to offer full turn-key test systems. These systems can broadly be categorized as far-field or near-field test systems, and NSI-MI has implemented them over a frequency range from 50 MHz to 1 THz.

All these test systems require the seamless integration of mechanical positioners, RF instrumentation, anechoic and environmental control, and a software suite to orchestrate the automated measurement acquisition. Although many of these systems are custom-designed and built, NSI-MI also has standardized common test systems to reduce cost and delivery times and can offer these systems as commercial off-the-shelf solutions akin to benchtop instruments.

NSI-MI’s most significant technological achievements include:

The development of high-capacity precision positioners—Allowing for the positioning of devices under test with weights ranging from 10 to 250,000 kg to within sub-milliradian angular positioning or to within twenty-micron linear positioning accuracies. This level of precise positioning allows NSI-MI to offer near-field test systems operational up to 1 THz and reduce measurement uncertainty to unprecedented levels.

Introduction of high-speed RF acquisition—NSI-MI RF subsystems are optimized for the application, and data throughput allows for high-speed on-the-fly acquisition while minimizing spatial positioning uncertainty. Parallelizing the NSI-MI multi-channel RF receivers creates a scalable solution that can accommodate the testing of multi-channel antennas, which is beneficial for characterizing phased array antennas where high data volumes are typical. Coupled with the antenna beam-steering computer, this solution allows for an efficient acquisition process to step the antenna through all beam states in a single acquisition cycle.

Compact range reflectors as part of our far-field product line—The design of these is well understood, however, the fabrication presents very significant challenges. NSI-MI developed a design and production capability to manufacture large reflectors as discrete panels. This ability enables a scalable solution that allows any reflector size to be container shipped worldwide and assembled on-site, with the mechanical fidelity to support test operation up to 100 GHz.

Sub-millimeter-wave near-field antenna testing—As frequencies increase, the mechanical precision required for high-fidelity measurements becomes a limiting factor. NSI-MI has developed structure correction techniques to compensate for practical structure limitations. As a result, we have successfully implemented near-field test systems that are being used up to 1 THz.

Computational electromagnetic expertise—Enables us to design anechoic chambers with optimized performance. This capability allows us to predict RF system performance before chamber construction. This also reduces chamber footprint and cost and allows for the optimization of absorber layout and size. Computational electromagnetic codes enable this expertise and represent a level of test system design that keeps NSI-MI at the forefront of technological advancements in the industry. 

MPD: An increasing number of applications rely on RF and microwave technology. What application stands out as the most likely to significantly contribute to the industry by the end of the decade?


Phased array technology must be considered in this regard. Although this technology has been used in the defense industry for decades, the efficiency improvement of active high-frequency RF components and cost reduction have made phased array technology ubiquitous. Add the increase in computational power that enables digital beamforming, and phased arrays offer a level of reconfigurability that makes the application options almost limitless.

This technology is well-established in the radar industry but has also found its way into cellular networks, cellular handsets, satellite ground stations, and autonomous vehicle applications. Higher power components further make phased array technology more attractive than ever and, coupled with radiation-hardened components, have even allowed for their deployment in space.

From an RF test perspective, phased arrays present a unique challenge. All these arrays require initial calibration through testing to start functioning. This process evaluates RF power linearity and phase adjustment ability to allow for beam focusing and steering. Doing this is typically very data-intensive, and having the ability of high data throughput is essential for an efficient test process. The NSI-MI test systems support this process seamlessly.